My personal opinion, its kind of a waste to change out midpipes only to go with another catted one.
Go no cats and keep the stock H laying around so you can swap it for emissions. The swap isnt hard the first time, only gets easier after that.
A Prochamber would sound great with Flows, as would an offroad H, even an X pipe if you like a different in your face agressive sound.
Im running a UPR X no cats with Mac Flowpaths. Everyone says "x pipe + chambered muffler = horrible", but ive changed alot of peoples minds.
Either way, if you want a deep classic muscle car tone, go with the Prochamber or H all the way. The X is something different.